Multiplexed Controllable Assembly Of Plasmonic Metal Nanoparticles And Their Applications

Metal nanoparticles have unique optical,electrical and magnetic properties,especially the localized surface plasmon resonance(LSPR)property,thus having wide applications in information storage,optoelectronic devices,biosensors,catalysis and other important fields.The LSPR property of metal nanoparticles can be flexibly regulated through adjusting shape,size,composition,interparticle distance,surrounding environment and other factors.The construction of assembled nanostructures on substrate surface using metal nanoparticles as building units can not only show the properties of the nanoparticles themselves,but also exhibit the excellent new physical and chemical properties generated by the whole nanostructures.However,single metal nanoparticle structure cannot meet the needs of multidisciplinary development.Therefore,one of the key issues to achieve current application requirements is being able to construct multiplex metal nanoparticle structures(different morphologies,sizes,compositions,spacings,arrangements,etc.)on one substrate,and realize precise regulation of structure and function.Till date,the ordered assembly of metal nanoparticles into designed structures and shapes can be controlled through the utilization of "bottom-up" self-assembly methods,such as solvent evaporation method,template-assisted method and molecular cross-linking method,as well as the use of weak interaction forces such as hydrogen bonding,electrostatic interaction,van der Waals force and hydrophobic-lipophilic interaction.Nevertheless,there still remains certain technical difficulties for achieving directional assembly of multiplex metal nanoparticle structures on one substrate by using single self-assembly method.Therefore,focusing on the electrostatic interaction between substrate surface and colloidal nanoparticles,the electrical changes on substrate surface are regulated through substrate charge inversion method,and the multiplex metal nanoparticle structures with different sizes,morphologies,distances and compositions are fabricated,thus realizing the regulation of their plasmonic properties and exploring their applications in information encoding and multiple detection.Detailed research contents include the following three aspects.(1)Since the assembly controllability of positively charged metal nanoparticles is relatively poor and traditional methods are hard to directly prepare uniform negatively charged substrate,a targeted method of charge inversion on substrate surface is developed.Through the amidation reaction between succinic anhydride and the amino groups on positively charged substrate,the carboxyl groups are uniformly grafted onto the substrate surface,and the inversion from positively charged substrate to negatively charged substrate is successfully realized.By controlling the time of amidation reaction,the electrical properties of substrate are precisely regulated and the controllable assembly of plasmonic nanoparticles with different sizes,charges and spacings are further realized.Research shows that such method is suitable for the two-dimensional assembly of metal nanoparticles with large areas,as well as the ordered assembly in templated patterns.Overall,a simple and efficient approach is provided for the preparation of substrates and the controllable assembly of metal nanoparticles,which lays the foundation for the multiplexed assembly of metal nanoparticles and the regulation of their properties(2)Utilizing the method of substrate charge inversion,stable substrates with negative charges are prepared and multiplexed assembly of gold nanoparticles with different morphologies on one substrate is realized,which is successfully applied to information encoding and decoding.Au nanosphere arrays and peanut-like Au nanorod arrays are defined as signal "0" and signal "1" separately,and three different signal combinations,"0-1-0","1-0-1" and "0-0-1" are designed.With the help of dark-field scattering microscope,these signals are further quickly,accurately and efficiently recognized.In addition,such strategy has strong universality and can be extended to the multiplexed assembly of various metal nanoparticles with different sizes,shapes and compositions,providing new opportunities for the practical applications of plasmonic nanostructures.(3)Multiplexed assembly of two metal nanoparticles with different compositions on one substrate is realized and then applied to multiple detection and analysis.By choosing suitable nanoparticles and designing reasonable templates,periodic interval arrays of Au nanospheres and Au@Ag nanorods are constructed under suitable parameter conditions,and subsequently the selective fluorescence enhancement responses of eosin Y(green)and crystal violet(red)are observed.Combining with plasmon-enhanced fluorescence mechanism,the experimental phenomena and results are analyzed and explained,providing guidance for optimizing the construction of metal nanoparticle structures and effects of selective fluorescence enhancement.In addition,this method is expected to be applied to anti-counterfeit labels and biomolecular detection.